Switchgear assembly

ABSTRACT

Switchgear is provided that includes a housing enclosing electrical components having switch blades that establish visible open gaps in an open position. The switchgear includes an array of operating controls and viewing provisions to observe the open switch blades. The operating controls and viewing provisions are accessible from a first direction and are arranged at a first area of the housing while cable interconnection provisions are accessible from a second direction and are arranged at a second area of the housing. Thus, operating personnel can utilize the viewing provisions and the operating controls without being exposed to the area of the cable interconnections. In one specific arrangement, an array of operational displays is provided, with the displays overlying the viewing provisions and being movable to permit use of the viewing provisions. In a preferred arrangement, the switchgear includes multi-pole switchgear assemblies which are assembled from individual pole-unit assemblies. The multi-pole switchgear assemblies are mounted to a housing along a single edge or corner of the switchgear assembly.

CROSS REFERENCE TO RELATED APPLICATION

This is a division of application Ser. No. 08/705,460 filed on Aug. 29,1996, now U.S. Pat. No. 5,864,107.

This application is a continuation-in-part of application Ser. No.08/653,176 filed May 24, 1996 abandoned in the names of B. B. McGlone etal.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to switchgear for the field ofelectrical power distribution, and more particularly to switchgear thatfacilitates most operations without exposure to the high voltageenvironment adjacent cable terminations and the like.

2. Description of the Related Art

Switchgear are generally categorized by various categories and featuressuch as: installation location (e.g. grade or surface, sub-surfaceetc.); the configuration of components (e.g. load interrupter switches,fuses, fault interrupters, disconnects, sectionalizers, etc.); the cableconnections (e.g. elbows, cable terminators); the accessibility ofcomponents and controls; the medium within the switchgear enclosure, forexample air, vacuum, oil, gas (such as SF₆), etc.; and additionalfeatures such as fault indicators, voltage indicators, power operation,automatic fault interruption control, etc. For example, switchgear thatincorporate the combination of a vacuum interrupter with a seriesconnected visible disconnect is disclosed in U.S. Pat. No. 4,484,046 andillustrated in the Square D Bulletin SY-9T (9/86). In the arrangement ofthe aforementioned U.S. Pat. No. 4,484,046, the visible disconnect isalso connected to a ground when moved to the opened position. Anotherarrangement, Type RGC switchgear available from ABB and illustrated inCatalog publication N-H 5194 E, utilizes a loadbreak switch and seriesconnected disconnect that is visible and connected to ground in an openposition, the loadbreak switch and the disconnect being disposed in anSF₆ environment. Another arrangement disclosed in U.S. Pat. No.5,508,486 is directed to gas-insulated switchgear having exit passagesand a drive device for the internal multi-pole vacuum switch andmulti-pole circuit breaker arranged on a front wall of the switchgearhousing, the vacuum switching tubes being arranged at right angles tothe front wall and the axis of rotation of the switch shaft of thecircuit breaker being horizontal and parallel to the front wall of thehousing.

While these prior art arrangements may be useful to provide switchgearof various configurations, the prior arrangements are rather awkward tooperate and require exposure to the area of the high-voltage cables, donot offer desirable viewing of the open gap of the internal switches,and do not include basic configurations or features that permit theswitchgear to be installed in different environments and in differentmounting configurations. Switchgear that alleviates many of thesedrawbacks is shown in U.S. Pat. No. 5,521,567. However, additionaloperational and structural features would be desirable to enhance theusability and producability of this type of switchgear.

SUMMARY OF THE INVENTION

Accordingly, it is a principal object of the present invention toprovide a desirable configuration of switchgear for ease of operationand viewing of the open gap of internal switches without exposure to anyhigh-voltage.

It is another object of the present invention to provide switchgear thatincludes arrays of viewing windows, movable informational displays thatoverlie the viewing windows, and operating controls that are allaccessible without any exposure to cable interconnections.

It is a further object of the present invention to provide switchgearthat has excellent producability characteristics, ensures the accuratealignment of components and is adaptable to provide a variety ofcomponent configurations.

It is yet another object of the present invention to provide switchgearcomponent assemblies that are easily assembled from pole-unitassemblies, such that different configurations are easily achieved.

It is an additional object of the present invention to providemulti-pole switchgear assemblies that are adapted for mounting from asingle edge of the assemblies such that an array of such multi-poleassemblies are mounted within a housing on a narrow planar surface.

These and other objects of the present invention are efficientlyachieved by the provision of switchgear including a housing enclosingelectrical components having switch blades that establish visible opengaps in an open position. The switchgear includes an array of operatingcontrols and viewing provisions to observe the open switch blades. Theoperating controls and viewing provisions are accessible from a firstdirection and are arranged at a first area of the housing while cableinterconnection provisions are accessible from a second direction andare arranged at a second area of the housing. Thus, operating personnelcan utilize the viewing provisions and the operating controls withoutbeing exposed to the area of the cable interconnections. In one specificarrangement, an array of operational displays is provided, with thedisplays overlying the viewing provisions and being movable to permituse of the viewing provisions. In a preferred arrangement, theswitchgear includes multi-pole switchgear assemblies which are assembledfrom individual pole-unit assemblies. The multi-pole switchgearassemblies are mounted to a housing along a single edge or corner of theswitchgear assembly.

BRIEF DESCRIPTION OF THE DRAWING

The invention, both as to its organization and method of operation,together with further objects and advantages thereof, will best beunderstood by reference to the specification taken in conjunction withthe accompanying drawing in which:

FIG. 1 is a perspective view of switchgear according to a firstembodiment of the present invention;

FIG. 2 is a right-side elevational view of the switchgear of FIG. 1partly in section and with parts cutaway for clarity;

FIG. 3 is a diagrammatic representation of the switchgear of FIGS. 1 and2 illustrating the features and operation of the switchgear;

FIG. 4 is a perspective view of a second embodiment of switchgearaccording to the present invention;

FIG. 5 is a diagrammatic representation of the layout of a display forthe switchgear of FIG. 4;

FIG. 6 is a left-side elevational view of the switchgear of FIG. 4partly in section and with parts cutaway for clarity;

FIGS. 7-9 are respective top plan, and front and right-side elevationalviews of the display of the switchgear of FIGS. 4 and 6;

FIGS. 10-12 are respective perspective, front elevational and top planviews of a multiple pole-unit assembly of the switchgear of FIGS. 4 and6;

FIG. 13 is a perspective view of a mounting channel for the multiplepole-unit assembly of FIGS. 10-12;

FIG. 14 is a perspective view of a pole-unit assembly of the multiplepole-unit assembly of FIGS. 10-12;

FIG. 15 is a perspective view of the pole-unit assembly of FIG. 14 withone of the support sheets removed for clarity;

FIG. 16 is a partial perspective view of a pole-unit assembly similar toFIGS. 14 and 15, but with additional features for a higher operatingvoltage;

FIG. 17 is a partial perspective view of a pole-unit assembly similar toFIGS. 14 and 15 but including a fault interrupter;

FIGS. 18 and 19 are perspective views of respective top and bottomhousing portions of the housing for the switchgear of FIGS. 4 and 6;

FIG. 20 is an elevational view partly in section and with parts cut awayfor clarity illustrating a separation spacer of the switchgear of FIGS.1-19;

FIG. 21 is a diagrammatic illustration of dielectric stress utilizingconventional fastening and support methods;

FIGS. 22 and 23 are top plan and right side elevational views,respectively, of the separation spacer of FIG. 20;

FIG. 24 is a diagrammatic illustration of the separation spacer of thepresent invention of FIG. 20; and

FIG. 25 is a block diagram electrical schematic diagram of portions ofthe display and testing features of the switchgear of FIGS. 4-19.

DETAILED DESCRIPTION

Referring now to FIGS. 1-3, the switchgear 10 of the present inventionprovides various predetermined configurations/combinations of loadinterrupter switches and resettable fault interrupters in a switchgearlineup having a pressurized, gas-filed volume within a housing 200. Thehousing 200 is an elongated, monocoque shell with a polygonalcross-section to provide suitable clearances and predetermined functionsin structural strength, mounting and supporting the various components,e.g. the load interrupter switch 202 illustrated in FIG. 2.

The switchgear 10 defines one or more viewing windows, e.g. 204, along atop surface 206 of the housing 200, preferably arranged as an alignedrow or first array 205 with one viewing window, e.g. 204, alignedimmediately above one or more switch blades 203 of each load interrupterswitch 202 or other switch component. For example, as shown in FIG. 2,viewing windows 204, 208, 210, and 212 are arranged above a respectivelineup of a first load interrupter switch, a resettable faultinterrupter, and second and third load interrupter switches. A secondaligned row or second array 215 of controls, e.g. illustrative operationselectors 214, 216, is also provided along the top surface 206 of thehousing 200. The second array 215 is spaced apart from the first array205 of the viewing windows, with the general directions definedgenerally by each of the arrays 205 and 215 being generally parallel.

The operation selectors such as 214, 216 are utilized to operate theload interrupter switches and resettable fault interrupters via aremovable handle 244 shown in FIG. 6. As shown in FIG. 2, the operationselector 216 is for operation of a three-pole load interrupter switchand the operation selector 214 is for operation of a disconnect functionof one pole of a three-pole resettable fault interrupter. It should alsobe understood that in other arrangements, the third array 215 alsoincludes indicators, test features etc. A control housing 217 extendingto the rear of the housing 200 is provided for trip control ofresettable fault interrupter components.

The switch blade 203 is shown in the closed position in FIG. 3. The openposition of the switch blade 203 is referenced at "O" while a third,ground position is referenced at "G". The plane of rotation defined bythe operating positions of the switch blade 203 is generallyperpendicular to the top surface 206. The switch blades 203 are operatedvia linkage generally referred to at 246 connected to a switch operatingshaft 248. The switch operating shaft 248 is driven by an operatingmechanism generally referred to at 250 and operated by the operationselector 216 through an operating shaft 242. The switch operating shaft248 is arranged generally parallel to each of the top surface 206 andthe front surface 224.

The switchgear 10 also includes a third aligned row or third array 218of external interconnections such as bushings 220 for connection toelbow connectors or the like which terminate power distribution cablesof an electrical power distribution system. The third array 218 ofexternal interconnections provides electrical connection to the variousinternal electrical components such as each pole of the load interrupterswitches 202 and resettable fault interrupters. The third array 218 ofbushings 220 is arranged generally along the front surface 222 of thehousing 200, and more specifically in a preferred embodiment, along asurface 224 that is inclined with respect to the generally verticalfront surface 222. In a preferred embodiment, the general directiondefined generally by the third array 218 is generally parallel to thefirst and second arrays 205, 215.

Accordingly, the first array 205 of the viewing windows and the secondarray 215 of the controls are arranged along a first surface 206 of thehousing 200 and the third array 218 of bushings 220 for cableinterconnection provisions (e.g. to connect to elbows on cables) arearranged along an angled frontal surface 224, spaced away from andforming an angle "a" with respect to the surfaces on which the first andsecond arrays 205 and 215 are located. The angle "a" can be referred toas being generally perpendicular. In one specific arrangement, the angle"a" is approximately 100 degrees, while a range of 90-110 degrees hasbeen found desirable. The first and second arrays 205 and 215 of viewingwindows and controls can also be characterized as being accessible froma first direction and being arranged at a first area of the housing 200,while the third array 218 of external interconnections is accessiblefrom a second direction and is arranged at a second area of the housing200. Of course, it should be realized that the first array 205 can becharacterized as being located at a first area, the second array 215being located at a second area, and the third array 218 being located ata third area, where the first and second areas are each accessible fromthe first direction and the third area is accessible from the seconddirection.

In this way, and in accordance with important aspects of the presentinvention, the switchgear 10 provides desirable operatingcharacteristics and convenient operation in various mountingorientations and environments. Thus, viewing of the position of theswitch blades 203 through the viewing windows, e.g. 204, and operationof the switch blades 203 via the controls, e.g. operation selector 214,may be performed from a first position with respect to the top surface206. From that first position, there is no exposure to or anyinterference from the cable terminations on the bushings 220. Further,handling of the cables on the bushings 220, e.g. for connection anddisconnection of the elbows, may be performed from a second convenientposition at the front of the switchgear 10.

For example, referring to FIG. 3, operating personnel at 228, can viewthe open position of the switch blade 203 from a position above theswitchgear 10 generally along a first direction generally referred to at252 while standing on a surface referred to generally at 226. Thecontrols, e.g. operation selector 214, may be operated and/or theviewing windows, e.g. 204, may be utilized from a kneeling or crouchingposition. If the switchgear 10 is located in a pit below the surface226, viewing into the switchgear 10 and operating the controls (e.g.operation selector 214) of the second array 215 may be performed fromthe surface 226 without entering the pit and without being exposed tothe environment of the bushings 220 and associated cables. Further, ifit is desired to disconnect the cables from the bushings 220, theoperating personnel may manipulate the cables with a shotgun stick orthe like while standing on the surface 226 from a position at the frontof the switchgear generally along a second direction referred togenerally at 254, i.e. the second position referred to above. Theseoperations are performed without entering the pit. Reference may be madeto the aforementioned copending application Ser. No. 08/653,176 filedMay 24, 1996 in the names of B. B. McGlone et al. for a more detaileddiscussion of operation with respect to the switchgear in a pit. Theswitchgear 10 may also be arranged such that the top surface 206 withthe arrays of viewing windows and controls is generally vertical whilethe bushings 220 are arranged to so as to generally be oriented upwardor downward for convenience of operation.

Of course, in other arrangements, it should be realized that theswitchgear 10 is further arranged inside an enclosure of the varioustypes available for pad-mounted gear. For example, as shown in FIG. 1,lower end panels with support legs 230, 232 are provided on the housing200 for use in an enclosure or for mounting on a surface. Additionally,upper end panels with lifting brackets 234, 236 are provided for use intransporting and maneuvering the switchgear 10. The housing 200 may befabricated either from various metals (e.g. 7-gauge mild steel) orinsulating materials, as suitable for the specific structural supportrequirements.

Thus, the switchgear 10 via the predetermined configuration of thehousing 200 and the arrangement of the third array 218 of externalinterconnections, the first array 205 of viewing windows, and the secondarray 215 of controls provides a versatile switchgear lineup thatfacilitates desirable operating characteristics and that is capable ofbeing mounted in various desirable configurations and orientations. Forexample, with the switchgear 10 located in a pit in the relativeposition as shown in FIG. 3, operating personnel can perform alloperations such as switching, isolating, grounding, voltage testing andphasing without any exposure or access to the high voltage areas. Thisis possible since direct observation of the position of the switchblades 203 and access to the operating controls are readily available bypersonnel from above ground and from the first direction 252. For thoseoperations that require elbow/cable manipulation via a hot stick or thelike, access is from the front of the switchgear from the seconddirection 254.

As disclosed in the aforementioned U.S. Pat. No. 5,521,567, theswitchgear 10, in a preferred embodiment, also includes a completeinternal and integral system to satisfy desirable operating practices todeenergize, test and ground the circuit before working thereon.

Considering now other important aspects of the present invention andreferring now additionally to FIGS. 4-9, the switchgear 20 of FIG. 4additionally includes one or more displays, e.g. 24 which provideinformation about the status of the circuit and components of theswitchgear 20. The displays such as 24 are located along the top surface206 of the housing 200, preferably arranged as an aligned row or fourtharray 26, with one display, e.g. 24, so as to overlie (i.e. alignedimmediately above) one of the viewing windows, e.g. 204. For example, asshown in FIG. 4, displays 24, 28, 30, and 32 are arranged above therespective viewing windows 204, 208, 210 and 212. The displays 24, 28,30, and 32 are pivotally mounted along an axis 34 with respect to thehousing 200 such that the displays 24, 28, 30 and 32 may be lifted topermit observation through the respective windows 204, 208, 210, and 212with an observer positioned over the controls of array 215, e.g. fromthe first direction 252 as shown in FIG. 3. In this manner, with thedisplays as shown in FIG. 4, circuit conditions may be ascertained viathe information on the displays, while in the open position, indicatedat 24' in FIG. 4 and 6, the position of the switches may be directlyobserved. Further, the displays 24, 28, 30 and 32 when in the closedposition of FIG. 4 also function as flashcovers over the respectivewindows 204, 208, 210 and 212, e.g. to avoid any flash effect throughthe windows to observers that may occur during switching operations whenfault conditions are present.

As seen in FIG. 6, the window 204 is assembled to provide a seal to thehousing 200 via a frame member 44 around the perimeter of the window 204and clamps 46 which clamp the frame member 44 and the window 204 againstthe inner surface of the housing 200, a sealing agent or the like beingprovided between the top surface of the perimeter of the window 204 andthe housing 200. The clamps 46 are secured to the housing 200 viathreaded studs 47 extending from the housing 200 and passing through theclamps 46 and nuts 48 threaded onto the studs 47 to provide appropriateclamping forces.

In a specific arrangement, each of the displays 24, 28, 30 and 32includes a display panel 40 with various indicia and indicators torepresent the energized/deenergized status of each pole of the overliedload interrupter switch or fault interrupter. For example, adiagrammatic representation of the layout 50 of the indicia andindicators of an illustrative display panel 40 is shown in FIG. 5.Specifically, each pole includes a voltage indicator 52 and a linediagram 54 representing the electrical circuit and the load interrupterswitch or fault interrupter (a load interrupter switch being illustratedin FIG. 5). A test indicator 60 and the voltage indicator 52 provideinformation on the operable status of the display panel 40 and theintegrity of the voltage sensing system for each pole. Reference may bemade to the aforementioned U.S. Pat. No. 5,521,567 for a furtherdiscussion of the testing of the integrity of the voltage sensingsystem. Voltage sensing and circuit testing signals are provided viaconductors in a cable 241 (FIGS. 4 and 6) for each of the display panels40, the cable 241 being connected to a sensor (not shown) arranged atthe cable terminations 220.

In the illustrative example of the display panel 40, the test indicator60 displays a predetermined test symbol, e.g. a solid circle, when thedisplay panel 40 is appropriately sequenced for testing. In the specificillustration, for testing purposes, the display 24 is powered by a solarpanel 64. Additionally a test actuator 66 is provided that includes atransparent window over an optical switch at 66. The display panel 40 isarranged to actuate a test sequence in response to the blocking of lightto the optical switch at 66 while the solar panel 64 is illuminatedsufficiently to provide power to actuate the display panel 40 and testcircuit. Thus, after the user covers the test actuator 66, the displayof the test symbol in the test indicator 60 provides assurance that thedisplay panel 40 is appropriately powered up and fully functioning. Withthe test indicator displayed at 60, the user may then ascertain theoperability of each voltage indicator 52 and the integrity of thevoltage sensing circuit for that corresponding pole.

In a specific embodiment, the voltage indicator 52 flashes the energizedsymbol, e.g. lightning bolt or the like, in the test mode to verify thatthe voltage indicator 52 is functional and the voltage sensing circuitis fully functional and reliable. Following this test function, i.e.after the operator unblocks the transparent window over the opticalswitch at 66, the energized/deenergized status of each pole may then beascertained via the status of the voltage indicator 52 provided for eachrespective pole, for example 52b and 52c for the respective second andthird poles of the display panel 40. In a specific embodiment, while thevoltage indicators 52 are arranged for normal functioning, the operatorbefore relying on the absence of an energized symbol at the voltageindicator 52, activates the testing mode of the display 40 via thefeature at 66 and observes the test symbol at 60 and checks for thepresence of the energized symbol at 52 to determine proper operation.Without such appropriate testing, the voltage indicators 52 inthemselves would function only as ordinary indicators as found in theprior art.

Referring now additionally to FIG. 25, the testing circuit 90 of thedisplay panel 40 is powered by the solar panel 64 and actuated by thetest actuator feature at 66. When the optical switch 92 is turned off bythe blocking of light at 66, the optical switch 92 via path 94 activatesa power regulator stage 96. The power regulator stage 96 supplies powerto the power converter and signal generator stages referred to at 98which actuate the test indicator 60 with a suitable alternating wavesignal at 100. The alternating wave signal at 100 via a surge protectionstage 102 provides signals for each phase at 104 which are connected tothe testing line routed over the cable 241 (FIGS. 4 and 6) to thebushing sensors 105 located at the terminations 220. This signal pathtests the integrity of the overall sensing circuit. If the sensing pathis fully functioning, the signal will be returned at 106 on the linesfrom the bushing sensors 105. The signal at 106 is then processed by apower condition and logic stage 108 which provides protection and thedesired indicator waveform at 110 to drive the voltage indicator 52,e.g. a flashing signal. Accordingly, the testing circuit 90 of thedisplay 40 when actuated by the test actuator feature at 66 checks theintegrity of the signal paths from the sensor and activates the voltageindicators at 52 to also test the integrity of the voltage indicators52. As discussed hereinbefore, if the voltage indicator 52 is notactuated during the testing mode with the testing indicator actuated,the operator is alerted that the voltage indicators 52 are not workingand not to be relied upon.

Referring now to FIGS. 7-9 and considering the specific structure of anillustrative display 24, the display 24 includes a cover member 70 thatis preferably fabricated as a molded part and provides a receptacle 72for the display panel 40. A trailing edge 74 of the cover member 70includes a sloped, upstanding lip 76 which is arranged to contact thetop surface 206 of the housing 200 when pivoted to define a stop for theopen position of the cover member 70 and display 24. Along the trailingedge 74, the cover member 70 also includes pivot bearing holes 78, 80for receiving pivot pins 82 (FIG. 6) along the axis 34, the pivot pins82 being supported by flange members 83 extending from the housing 200.

Referring now additionally to FIGS. 10-13 and in accordance withimportant aspects of the present invention, in a preferred embodimentthe load interrupter switch 202 is provided as a multiple pole-unitassembly, e.g. as specifically illustrated in FIGS. 2 and 3, the loadinterrupter switch 202 includes three poles. The load interrupter switch202 is suspended with respect to the housing 200 via a support channel270 (FIGS. 2, 6 and 13). The support channel 270 (best seen in FIG. 13)is affixed to the inner wall of the top surface 206 of the housing 200(FIG. 6). The load interrupter switch 202 is affixed to the supportchannel 270 (FIG. 6) via fasteners 272 which are threaded into threadedsleeves 273 in the support channel 270. As seen in FIGS. 10-12, thefasteners 272 extend through apertures 274 in a mounting flanges 276 ofthe operating mechanism 250 and additional mounting flanges, e.g. 278,280 and 282 of the load interrupter switch 202. As seen in FIG. 6, theoperating shaft 242 extends through the support channel 270 and the topsurface 206 of the housing 200 via an aperture 243, shaft 242 alsoincluding suitable seals not shown in detail.

It should be noted that the mounting of the load interrupter switch 202from a single edge or corner of the overall generally rectangularparallelepiped assembly not only simplifies assembly and allowsflexibility in the configuration of the assembly 202, it also minimizesthe structural rigidity requirements for the housing 200 relating toalignment and mounting of components. Additionally, this techniquepositions the assembly 202 centrally of the interior of the housing 200while also providing support and alignment for the operation selectors216 and the operating shaft 242 that drives the operating mechanism 250.In order to achieve the desired structural rigidity with particularmaterials. one or more ribs 240 may be provided along the top of thehousing 200 as shown in FIGS. 4 and 6. Where such ribs 240 are provided,the rib 240 may also be utilized to support the pivot pins 82 of thedisplay, e.g. 28, in lieu of the flange members 83.

In accordance with important aspects of the present invention and withreference to FIG. 10, to enhance the visibility of the switch blade 203in the various positions, i.e closed, open and ground, and especiallythe open position to observe the visible open gap, the load interrupterswitch 202 includes openings 290 arranged in a predetermined manner, andadditionally, the colors of the various components of the loadinterrupter switch 202 are selected to enhance visibility. For example,support sheets 301, 303 are black, blade portions 292 of the switchblade 203 are silver, and portions 294 of the switch blade 203 areorange. Thus, in this manner, the silver color of the blade portions 292are easily visible and the orange portions 294 assist to focus on theposition of the open gap.

Turning now to a more detailed discussion of the individual pole unitsof the load interrupter switch 202, the load interrupter switch 202includes three pole-unit assemblies 296, 298 and 300, the center poleunit 300 including the operating mechanism 250. Referring nowadditionally to FIGS. 14-15, the illustrative pole unit 300 includes thesupport sheets 302, 304. The support sheets 302, 304 are non-conductiveand arranged so as to be spaced apart and generally parallel to eachother with components and interconnections mounted between and withrespect to the support sheets 302, 304. The support sheets 302, 304 arespaced apart and fastened to each other by spacer arrangements generallyreferred to at 309, e.g. as specifically illustrated in FIG. 15, sleeves308 and bolts 310 passing therethrough.

Thus, the support sheets 302, 304 support and provide accurate alignmentfor and between the components as well as provide electrical isolationbetween the support points of the illustrative pole-unit assembly 300.In addition to the switch blade 203, the components of the pole unit 300include a stationary contact assembly 320, a bus-interconnectionconductor 322 that is provided for interconnecting the stationarycontact 320 to a through bus (not shown) of the lineup, aninterconnection assembly 324 for connecting the movable switch blade 203to the bushing 220, and a ground interconnection assembly 326.Additionally, the operating mechanism 250 is attached to the pole unit300 via fasteners cooperating with extending tabs 330 of the operatingmechanism 250 and a support and guide bracket 332 affixed to theoperating mechanism 250 and affixed between the support sheets 302, 304via fasteners. An operating-spring housing 334 is carried by the supportand guide bracket 332. The operating-spring housing 334 includes acharging link 336 connected to the operating mechanism 250 and a drivelink 338 that provides input drive force to the operating mechanism 250.

Considering now in more detail the load interrupter switch assembly 202,the 3-pole, load interrupter switch assembly 202 is formed by combiningand fastening together three pole-unit assemblies 296, 298 and 300,which are appropriately spaced apart and fastened together by thefastening arrangement generally referred to at 350. Additionally,pole-to-pole spacer/support arrangements 352, 354 are provided betweeneach of the respective pole unit assemblies 296 and 298 and locatedapproximately midway along the rear (left in FIG. 12) edge of the poleunit assemblies.

In accordance with important aspects of the present invention, thespacer arrangements 309, pole-to-pole spacer/support arrangements 352,354, and the fastening arrangement 350 are varied in dimensions inspecific embodiments of the present invention to provide loadinterrupter switches having different operating voltage specificationsand different basic insulation levels, e.g. in the range of 95-150 kV.Additionally, and with additional reference to FIG. 16, the loadinterrupter switch of FIGS. 10-15 is provided with an additional phasebarrier 360 to achieve a higher voltage rating for the load interrupterswitch 202 via spacer arrangements 362 affixed to the support sheet 301,a phase barrier 360 additionally being provided between each of the poleunit assemblies 296, 298 and 300, as well as the outside of the poleunit assembly 296. In a specific embodiment, a cylindrical arc runner364 is also added at the main stationary contact 326 (FIG. 14).

Referring now additionally to FIG. 17, the switchgear of the presentinvention also includes fault interrupters, one pole assembly 370 ofwhich is shown in FIG. 17, with one of the support sheets 372 removedfor clarity. The fault interrupter pole assembly 370 is similar to theload interrupter pole unit assembly 300 of FIGS. 10-15, with theassembly 370 further including a vacuum interrupter 374, an actuatorlinkage 376, and a fault interrupter operating mechanism that is similarto the operating mechanism 250 but additionally includes a faultinterrupter output at 380 to operate the fault interrupter 374.Reference may be made to U.S. Pat. No. 5,504,293 for a more detaileddiscussion of these types of operating mechanisms. The main stationarycontact at 380 is connected via arrangement 382 to a first contact 384of the fault interrupter 374, a second contact 386 of the faultinterrupter 374 being connected to a pole bus arrangement at 388. Theremaining parts and components of the pole unit assembly 370 aregenerally similar to the pole unit 300.

Since the support sheets of the pole units (e.g. the support sheets 302,304 of the pole unit 300) support and mount energized and groundedcomponents on the same pole unit, dielectric stress is a factor thatmust be considered. For example, referring now to FIGS. 20-21, with theillustrative energized component 390 and the illustrative groundpotential component 392 mounted in the range of 4-5 inches apart on thesupport sheet 302, dielectric stress occurs at the mounting locationsgenerally referred to at 394, 396. As illustrated in FIG. 21, ifconventional metallic fasteners such as the bolt 398 are used to mountthe components, high stress occurs in a relatively small gap referred toat 391. This dielectric stress reduces the maximum operating voltage andbasic insulation levels.

Considering now additional important aspects of the present invention toreduce dielectric stress at the mounting locations of the componentswithin each of the three pole-unit assemblies 296, 298 and 300 of theload interrupter switch assembly 202, separation spacers 393 areprovided at the mounting locations 394, 396. Conventional fasteners 398are disposed through the separation spacers 393. Referring nowadditionally to FIGS. 22-23, the separation spacers 393 include awidened shielding ring 395 and a narrowed sleeve portion 397 thatfunctions as a separation member. Both the widened shielding ring 395and the narrowed sleeve portion 397 are conductive. With thisarrangement, and referring now additionally to FIG. 24, the dielectricstress in the gap 391 at the support sheet 302 is reduced with thewidened shielding ring 395 preventing the concentration of stress at thegap 391. It has been found that a suitable reduction in dielectricstress is achieved with the overhang of the widened shielding ring 395referred to at 399 being in the range of one to two times the width ofthe narrowed sleeve portion referred to at 401. As seen in FIG. 22,preferably the separation spacer 393 includes a knurled sleeve portion403 which provides increased retention and stability of alignment of thecomponents. While not necessary to make and use the invention, it istheorized that the widened shielding ring 395 combined with theseparation distance 401 shields the gap at 391 formed between the wallof the supporting sheet 302, the component 390, and the surroundingfluid environment, i.e. at the triple point of the interface.Accordingly, the separation spacers 393 are utilized in the pole-unitassemblies 296, 298 and 300, e.g. at locations 309 in FIG. 15.

Considering now the assembly of the switchgear 10 and 20, and referringnow additionally to FIGS. 18 and 19, the housing 200 is provided by atop housing portion 400 and a bottom housing portion 402. The upper endpanels 236, 238 are affixed to the upper housing portion 400, and thelower end panels 230, 232 are affixed to the sides of the lower housingportion 402. After the various pole unit assemblies such as the loadinterrupter switch 202 are mounted within the upper housing portion 400via the mounting channels 270, and the desired electrical connectionsare made to the terminations 220 and the desired interbus connectionsare made between the various pole unit assemblies, the upper housingportion 400, with the assembled pole unit assemblies, and the lowerhousing portion 402 are assembled, e.g. via welded along the seamsthereof. Then the assembly is sealed and pressurized with a suitableinsulating medium, e.g. SF₆ gas.

While there have been illustrated and described various embodiments ofthe present invention, it will be apparent that various changes andmodifications will occur to those skilled in the art. Accordingly, it isintended in the appended claims to cover all such changes andmodifications that fall within the true spirit and scope of the presentinvention.

What is claimed and desired to be secured by Letters Patent of theUnited States is:
 1. A pole-unit assembly for medium-voltage switchgearcomprising electrical components, at least two spaced apart generallyplanar support members, and means for supporting said electricalcomponents intermediate said two spaced apart generally planar supportmembers, said electrical components being operable at different voltagepotentials, said planar support members being non-conductive, and saidsupporting means comprising means for reducing dielectric stress at saidtwo spaced apart generally planar support members.
 2. A pole-unitassembly for medium-voltage switchgear comprising electrical components,at least two spaced apart generally planar support members, and meansfor supporting said electrical components intermediate said two spacedapart generally planar support members.
 3. The pole-unit assembly ofclaim 1 wherein said pole-unit assembly has a general overallrectangular parallelepiped shape and further comprises means formounting said pole-unit assembly with respect to a planar surface, saidmounting means being located along one edge of said pole-unit assembly.4. The pole-unit assembly of claim 1 wherein said electrical componentsof said pole-unit assembly comprise a multi-pole switch having two ormore operating positions and bus connection means for each pole of saidmulti-pole switch.
 5. The pole-unit assembly of claim 1 furthercomprising an operating mechanism for operating said electricalcomponents.
 6. The pole-unit assembly of claim 5 wherein said electricalcomponents of said pole-unit assembly comprise a multi-pole switchhaving two or more operating positions, said operating mechanismincluding means for operating said multi-pole switch between said two ormore operating positions.
 7. The pole-unit assembly of claim 6 whereinsaid pole-unit assembly has a general overall rectangular parallelepipedshape and further comprises means for mounting said pole-unit assemblywith respect to a planar surface, said mounting means being locatedalong one edge of said pole-unit assembly.
 8. The pole-unit assembly ofclaim 7 further comprising operating control means extending from saidoperating mechanism for controlling operation of said operatingmechanism.
 9. The pole-unit assembly of claim 8 wherein said mountingmeans is adjacent said operating control means.
 10. A pole-unit assemblyfor medium-voltage switchgear comprising electrical components, at leasttwo spaced apart generally planar support members, means for supportingsaid electrical components intermediate said two spaced apart generallyplanar support members, and means for enhancing the visibility of saidelectrical components including the color of said electrical componentsand the color of said generally planar support members.
 11. A pole-unitassembly for medium-voltage switchgear comprising electrical components,at least two spaced apart generally planar support members, and meansfor supporting said electrical components intermediate said two spacedapart generally planar support members, said electrical components beingoperable at different voltage potentials, said planar support membersbeing non-conductive and said supporting means further comprising meansfor providing a substantially conductive path from said electricalcomponents to said two spaced apart generally planar support members.12. The pole unit of claim 11 further comprising a plurality of saidspaced apart generally planar support members to define a multiple polecomponent assembly including said electrical components being mountedbetween respective pairs of said plurality of spaced apart generallyplanar support members.
 13. A pole-unit assembly for medium-voltageswitchgear comprising electrical components, at least two spaced apartgenerally planar support members, and means for supporting saidelectrical components intermediate said two spaced apart generallyplanar support members, said electrical components being operable atdifferent voltage potentials, said planar support members beingnon-conductive, and said supporting means comprising fastener means andmeans for reducing dielectric stress at said two spaced apart generallyplanar support members.
 14. The pole unit assembly of claim 13 whereinsaid dielectric stress reducing means comprises widened ring portionsextending from said fastener means adjacent said two spaced apartgenerally planar support members.
 15. A medium-voltage multiple-polecomponent assembly comprising a plurality of pole-unit assemblies eachoperative at different voltage potentials and means for assembling saidplurality of pole-unit assemblies in spaced apart relationship to eachother, each of said pole-unit assemblies comprising two spaced apartsupport members, electrical components operative at different voltagepotentials, and means for supporting said electrical componentsintermediate and with respect to said two spaced apart support members,said spaced apart support members being generally planar andnon-conductive, said supporting means comprising conductive fastenermeans.